数据加载器解析嵌套数组
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【中文标题】数据加载器解析嵌套数组【英文标题】：dataloader resolving nested array 【发布时间】：2019-04-08 11:52:39 【问题描述】：我有这种形式的架构
type User
id: String!
name: String
posts: [Post]
type Post
id: String!
userId: String
body: String
使用 facebook 数据加载器对请求进行批处理
query
GetAllUser
id
name
posts
id
body
这是我已经做过的
const GetPost = async function (root, params, context, info)
const userId = root.id;
const data = await loader.load(userId);
//console.log(userId, loader, data);
return data;
const loader = new DataLoader(userIds =>
return PostModel.find( userId: $in: userIds ).then(posts =>
const postsById = keyBy(posts, "_id");
console.log(postsById, posts)
const a = userIds.map(post => postsById[post]);
//console.log(userIds, posts, postsById, a);
return a;
);
);
如果我使用const postsById = keyBy(posts, "_id");，它返回[ undefined, undefined, undefined ] as a，如果我返回const postsById = keyBy(posts, "userId");，它返回
[ media: [],
reaction: [],
comment: [],
_id: 5bdef792bea4733c64bf5fee,
body: 'Today is sunday, we give God praise',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-04T13:43:46.253Z,
updatedAt: 2018-11-04T13:43:46.253Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdd949090d23c5aa430d575,
body: ' Ooop! going for a holiday soon',
privacy: 'public',
userId: 5bdd79ea0fef4004a040d110,
createdAt: 2018-11-03T12:29:04.385Z,
updatedAt: 2018-11-03T12:29:04.385Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdd8b5ea95dda4854c50d39,
body: 'i am a man',
privacy: 'public',
userId: 5bdd86dc1c76593b18a727db,
createdAt: 2018-11-03T11:49:50.244Z,
updatedAt: 2018-11-03T11:49:50.244Z,
__v: 0 ]
作为一个
但是console.log(posts)
posts:
[ media: [],
reaction: [],
comment: [],
_id: 5bda0d61c255f33550813a86,
userId: 5bd4dfa30a00291820c7896d,
body: 'I am very Happy today',
privacy: 'everyone',
createdAt: 2018-10-31T20:15:29.717Z,
updatedAt: 2018-10-31T20:15:29.717Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bda0d74c255f33550813a87,
userId: 5bd4dfa30a00291820c7896d,
body: 'Thank God for today',
privacy: 'everyone',
createdAt: 2018-10-31T20:15:48.218Z,
updatedAt: 2018-10-31T20:15:48.218Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bda0d86c255f33550813a88,
userId: 5bd4dfa30a00291820c7896d,
body: 'Deeka my bro',
privacy: 'everyone',
createdAt: 2018-10-31T20:16:06.042Z,
updatedAt: 2018-10-31T20:16:06.042Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdc03c4fec5eb3a4cfe2a57,
body: 'What are you saying',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-02T07:59:00.860Z,
updatedAt: 2018-11-02T07:59:00.860Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdc03d5fec5eb3a4cfe2a58,
body: 'What are you saying',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-02T07:59:17.672Z,
updatedAt: 2018-11-02T07:59:17.672Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdc0493fec5eb3a4cfe2a59,
body: 'Today is Beautiful',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-02T08:02:27.585Z,
updatedAt: 2018-11-02T08:02:27.585Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdc0493fec5eb3a4cfe2a5a,
body: 'Today is Beautiful',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-02T08:02:27.590Z,
updatedAt: 2018-11-02T08:02:27.590Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdc0493fec5eb3a4cfe2a5b,
body: 'What do u know about love',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-02T08:02:27.590Z,
updatedAt: 2018-11-03T03:06:04.308Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdc0493fec5eb3a4cfe2a5c,
body: 'Love is wicked',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-02T08:02:27.617Z,
updatedAt: 2018-11-03T03:04:27.168Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdc0ac953b24320885bb19d,
body: 'Today is really Beautiful',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-02T08:28:57.931Z,
updatedAt: 2018-11-03T02:48:57.201Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdd8b5ea95dda4854c50d39,
body: 'i am a man',
privacy: 'public',
userId: 5bdd86dc1c76593b18a727db,
createdAt: 2018-11-03T11:49:50.244Z,
updatedAt: 2018-11-03T11:49:50.244Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdd8db4702a272b14e5e4d3,
body: ' Ooop! going for a holiday soon',
privacy: 'public',
userId: 5bdd79ea0fef4004a040d110,
createdAt: 2018-11-03T11:59:48.279Z,
updatedAt: 2018-11-03T11:59:48.279Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdd949090d23c5aa430d575,
body: ' Ooop! going for a holiday soon',
privacy: 'public',
userId: 5bdd79ea0fef4004a040d110,
createdAt: 2018-11-03T12:29:04.385Z,
updatedAt: 2018-11-03T12:29:04.385Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdef776bea4733c64bf5feb,
body: 'Today is sunday, we give God praise',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-04T13:43:18.777Z,
updatedAt: 2018-11-04T13:43:18.777Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdef776bea4733c64bf5fec,
body: 'Today is sunday, we give God praise',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-04T13:43:18.782Z,
updatedAt: 2018-11-04T13:43:18.782Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdef776bea4733c64bf5fed,
body: 'Today is sunday, we give God praise',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-04T13:43:18.784Z,
updatedAt: 2018-11-04T13:43:18.784Z,
__v: 0 ,
media: [],
reaction: [],
comment: [],
_id: 5bdef792bea4733c64bf5fee,
body: 'Today is sunday, we give God praise',
privacy: 'public',
userId: 5bd4dfa30a00291820c7896d,
createdAt: 2018-11-04T13:43:46.253Z,
updatedAt: 2018-11-04T13:43:46.253Z,
__v: 0 ]
userIds 包含这个
userIds:
[ '5bd4dfa30a00291820c7896d',
'5bdd79ea0fef4004a040d110',
'5bdd86dc1c76593b18a727db' ],
正如你所看到的，我正在获取所有帖子，但是要为每个用户返回一个没有数据加载器的帖子数组，它正在使用以下代码
const GetPost = async function (root, params, context, info)
const post = await PostModel.find(
userId: root.id
).exec();
if (!post)
throw new Error('Post not found');
console.log(post)
return post;
解析器是posts: GetPost
【问题讨论】：
你的问题是为什么 Dataloader 会返回undefined 以获得某些结果？
@MikaelLirbank 抱歉，我的问题是将解析格式从这些 ` object, object, object ` 更改为 [[object, object], [object]]
【参考方案1】：
而不是这个加载器函数
const loader = new DataLoader(userIds =>
return PostModel.find( userId: $in: userIds ).then(posts =>
const postsById = keyBy(posts, "_id");
console.log(postsById, posts)
const a = userIds.map(post => postsById[post]);
//console.log(userIds, posts, postsById, a);
return a;
);
);
我用过这个
const loader = new DataLoader(userIds =>
return await PostModel.find( userId: $in: userIds ).then(posts =>
const allPosts = groupBy(posts, 'userId');
return userIds.map(post => allPosts[post] || []);
);
);
使用 loadash groupBy 得到的第一个结果将被格式化为
[[object, object, object], [object, object, object, object], [object]]
【讨论】：
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